This application is a 35 U.S.C. 371 National Stage filing of PCT/JP98/05368 filed Nov. 30, 1998.
The present invention relates generally to a carrier box for a semiconductor substrate, and in particular to a carrier box for receiving and carrying a substrate including a Si wafer, a glass substrate, a metal coated substrate or the like used in industries, such as the semiconductor industry, liquid crystal industry and precision machinery industry.
Air cleaning in a conventional clean room will be described with reference to FIG. 18 taking a case of air cleaning in a semiconductor manufacturing plant.
In FIG. 18, outside air 1 is passed through a pre-filter 2 to remove coarse particles, air-conditioned by an air-conditioner 3 and dedusted by a medium efficiency particulate air filter 4. Then small particles are removed by HEPA (high efficiency particulate air) filter 6 installed on a ceiling of a clean room 5 so that cleanliness class of 100 to 1,000 may be maintained in the clean room 5 (see xe2x80x9cClean Designxe2x80x9d pp. 11-24, summer of 1988). Each of reference numerals 7-1, 7-2 respectively designates a fan and an airflow is shown by arrows.
A conventional clean room is configured as shown in FIG. 18 since air cleaning therein purposes to remove particles. Though effective in removing particles, this configuration is of no effect in removing gaseous harmful components.
In addition, a large clean room as shown in FIG. 18 has a disadvantage in that it is excessively expensive to accomplish super cleanliness therein (xe2x80x9cBREAK THROUGHxe2x80x9d vol. 5, pp. 38-41, 1993).
It is of no doubt that, in the semiconductor industries, products will be continuously and increasingly required to be of higher quality and precision, and accordingly not only particles (particulate material) but also a gaseous material will be seriously regarded as a contaminant. That is, control of gaseous material (gaseous harmful component) will gain in importance while at present, removal of only particles is required. A conventional filter for a clean room as shown in FIG. 18 removes only particles, and a gaseous harmful component in outside air is introduced into a clean room without being removed thereby giving rise to a potential problem.
That is, in a clean room, adding to the particles (particulate material), a gaseous material such as an exhaust gas of automobile which cannot be collected and removed by a conventional dedusting filter (e.g. HEPA or ULPA filter) and is consequently introduced into the clean room, an organic gas or so-called hydro-carbon (H.C.) generated by an outgassing from a high molecular synthetic resin material which is extensive use, or a basic (alkaline) gas such as amine will become problematic as a gaseous harmful component.
Among these materials, H.C. is required to be removed since it causes contamination, even if it is of extremely low concentration in a normal atmosphere (indoor or outdoor air).
Recently, outgassing from high molecular synthetic resins of structural members of the clean room and instruments used therein (e.g. wafer storage box) has been discussed as a source of H.C. (xe2x80x9c1994 Annual Report of Japan Machinery Federationxe2x80x9d pp. 41-49, March of 1995).
The gaseous material generated by operation in a clean room also is problematic. That is, since a gaseous material generated in a clean room is added to that introduced thereinto from outside air (because the gaseous material cannot be removed by the filter of the clean room, gaseous material in the outside air is introduced thereinto) as a cause of origination of the gaseous material in a normal clean room, the gaseous material reaches a higher concentration in the clean room as compared with that in the outside air, and contaminates a base material of a wafer or a substrate.
That is, when the above contaminants (particles or gaseous harmful components) attach to a surface of a wafer or a partially or completely finished product, such contaminants may cause a breakage or short-cut in a circuit (pattern) on the surface of the substrate resulting in a failure. On the other hand, among gaseous materials, {circle around (1)} attaching to a surface of the wafer (substrate), H.C. increases a contact angle and affects an affinity (conformability) between the substrate and a resist. Deterioration of the affinity has a negative effect on a film thickness of the resist and on adhesion between the substrate and the resist (xe2x80x9cAir Cleaningxe2x80x9d vol. 33, No. 1, pp. 16-21, 1995). In addition, H.C. cause a pressure resistance deterioration (deterioration in reliability) of an oxide film of the wafer (Proceedings of the 39th Joint Lecture Meeting of Japan Society of Applied Physics, p. 686, 1992). {circle around (2)} NH3 causes a formation of ammonium salt and resulting a blooming on the wafer (deterioration in resolution) (xe2x80x9cThe Newest Technology Coursexe2x80x94Materialsxe2x80x94Semiconductor Process Seminar, Oct. 29, 1996xe2x80x9d pp. 15-25, Realise Corp., 1996).
Consequently, not only particles but also gaseous contaminants lower the productivity (yield) of the semiconductor products.
Especially, due to the causes of generation described above and further because of the promotion of air circulation in a clean room in recent years with a view to saving energy, the gaseous materials as gaseous harmful components in a clean room become condensed to a significantly higher concentration than that present in outside air, and attach to a base material or substrate and contaminate the surface thereof. A degree of contamination can be represented by the contact angle of the basic material or the substrate, that is, a greater contamination results in a larger contact angle. In a base material or substrate having a large contact angle, even if a film is formed thereon, an adhesive strength of the film is not sufficient (low conformability), and a lower yield results.
The term xe2x80x9ccontact anglexe2x80x9d used herein means a contact angle of wettability by a water and represents a degree of contamination on the surface of a substrate. That is, when a hydrophobic (oily) contaminant is attached to the surface of a substrate, the surface repels water, making it harder for it to be wetted. This results in an increased contact angle. Accordingly, a large contact angle indicates high contamination while a low contact angle indicates low contamination.
Especially, because recently air in a clean room is circulated to save energy, an amount of the gaseous harmful components in a clean room gradually increase and contaminate a base material and substrate.
As a measure to protect a substrate from contamination by these contaminants,
(1) transportation by a robot is effective. That is, since a person is a source of dust and gas, it is important to exclude any interposition thereof in order to maintain the cleanliness (xe2x80x9cMonthly Semiconductor World, Januaryxe2x80x9d pp. 112-116, 1997),
(2) From a viewpoint of cleaning, it is proposed that, in a future space cleaning, a local cleaning (mini environment) in which a clean space is limited (localized) will be effective ({circle around (1)} xe2x80x9cNikkei Microdevices, Julyxe2x80x9d, pp. 136-141, 1995, {circle around (2)} xe2x80x9cProceedings of IESxe2x80x9d, pp. 373-378, 1994).
Presently, though a system in which a Si wafer is received in a synthetic resin (plastic) box to be transported is being investigated as a mini environment, it is reported that (1) when unexpected dusting occurs within the box, particle contamination might become more serious, (2) a countermeasure for outgassing (gas generation) from the box material is required, and (3) a periodical cleaning process of the box itself is required because of (1) and (2) described above, which adds some complexity and causes some problems in practical use (xe2x80x9cKANOMAX Aerosol Seminarxe2x80x9d, pp. 1-10, 1996).
In the light of these problems, the inventors of the present invention have proposed a space cleaning system using a photo-electron or a photo-catalyst as a technology for local cleaning.
For example, 1) xe2x80x9cCleaning System by Photo-electron (removal of particulate materials)xe2x80x9d is disclosed in Japanese Patent Publication No. Hei 3-5859; Japanese Patent Publication No. Hei 6-74909; Japanese Patent Publication No. Hei 8-211; and Japanese Patent Publication No. Hei 7-121369, 2) xe2x80x9cCleaning System by Photo-catalyst (removal of gaseous harmful components)xe2x80x9d is disclosed in Japanese Patent Laid-open Publication No. Hei 9-168722; and Japanese Patent Laid-open Publication No. Hei 9-205046, and 3) xe2x80x9cCombined system of Photo-electron and Photo-catalyst (simultaneous removal of particles and gases)xe2x80x9d is disclosed in Japanese Patent No. 2623290.
These cleaning systems are effective depending on a type of object (or a kind of equipment to which these system are applied) or on a level of required performance, but in some cases usage thereof must be improved.
In making such improvements, there are some problems involved in making these systems more effective in their practical use. One of these problems arises from the fact that these systems make a gas clean by a flow method using heat generated by a light source of ultraviolet rays or the like. That is, depending on the type of object to which these systems are applied, it is important how to make the gas flow more effective and this includes a problematic mater to be improved.
Accordingly, in the light of the prior arts described above, the present invention provides a carrier box for a semiconductor substrate having a function to remove particles and gaseous harmful materials, which is effective in a practical use as a semiconductor substrate carrier box comprising a mini environment which is increasingly desired in industries such as semiconductor, liquid crystal or precise machinery industries, as the products thereof are required to be of more increasingly high quality, precision and have highly fine microstructures.
In order to solve the problems described above, the present invention provides a carrier box for a semiconductor substrate having an opening and closing mechanism for taking the semiconductor substrate in or out the box, said carrier box characterized by comprising a gas cleaning unit formed by integrating into one unit a gas cleaning device which uses a photo-electron or a photo-catalyst actuated by light irradiation for cleaning the inside of the box.
The present invention further provides another carrier box for a semiconductor substrate having an opening and closing mechanism for taking the semiconductor substrate in or out the box, said carrier box characterized by comprising a gas cleaning unit formed by integrating into one unit a gas cleaning device which uses a photo-electron or a photo-catalyst actuated by light irradiation for cleaning the inside of the box and a rechargeable battery-type electric power source device for supplying the gas cleaning device with electricity.
Preferably, the carrier box is made of a synthetic resin and the gas cleaning unit is provided with a heat radiator for transmitting heat generated in the electric power source device to the gas cleaning device when the electric power source device is integrally included in the gas cleaning unit.
In addition, when the electric power source device is not integrally included in the gas cleaning unit, the gas cleaning unit is supplied with electricity by being connected to an electric power supply device installed in a load port, a stand-by station or a stocker during an interval of the transportation of the carrier box (while the carrier box is not in use) and then is operated.
There will now be described the present invention with respect to the attached drawings.